The present invention relates to an Oldham ring which is one of parts constituting a scroll type compressor, and more particularly, to an Oldham ring which is the part serving to prevent a swivel scroll from revolving on its own axis.
In typical scroll type compressors, the swivel scroll is driven by a crank shaft so as to be caused to move in reciprocating motion within a plane parallel to a circular base plate of the swivel scroll. The circular base plate is formed in the bottom surface thereof with a pair of rectilinear guide grooves. An Oldham ring is disposed so as to be adjacent to and parallel with the circular base plate. The Oldham ring has a pair of first projections formed on one surface thereof adjacent to the circular base plate, the first projections being brought into engagement with the guide grooves. The Oldham ring also has a pair of second projections formed on the other surface thereof opposite to the surface on which the first projections are formed, the second projections being brought into engagement with a housing of the compressor so as to prevent the revolution of the Oldham ring. The swivel scroll is driven to reciprocate in the rectilinear direction along the pair of first projections while being restrained from moving in the direction of revolution of itself due to the engagement relationship between the guide grooves and the first projections.
In the conventional scroll type compressor, it has been general to employ a swivel scroll and an Oldham ring made of an iron system material. However, in order to reduce noise and friction loss caused due to high- o speed revolution, it has been hoped eagerly to reduce the weight of the swivel scroll and the Oldham ring of the scroll type compressor. Accordingly, reduction of weight has been realized by making the swivel scroll of aluminum as disclosed in JP-A-62-248887. Further, it has been proposed, for reduction of weight, to make both the swivel scroll and the Oldham ring of aluminum alloy. Namely, as disclosed in JP-A-2-283882, not only the swivel scroll and the Oldham ring has been made of aluminum alloy so as to reduce the weight, but also, as means for avoiding seizure, scuffing and abnormal wearing caused by the sliding movement between aluminum alloy members, an intermediate layer of iron-system material has been disposed in the engaging portion between the swivel scroll and the Oldham ring by thermal spraying the melt of the iron-system material thereto so as to ensure the high-speed revolution.
The method of treating the surface of the engagement portion between the swivel scroll and the Oldham ring as disclosed in JP-A-2-283882 encounters with the problems such as deterioration of the precision of parts caused as a result of treatment, additional cost resulting from the surface treatment, durability of the coating film and the like.